Device for driving shafts at a low and uniform speed by an electromotor



July 29, 1924. 1,502,958

' C. LOTT DEVICE FOR DRIVING SHAFTS AT A LOW A ND UNIFORM SPEED BY AN ELECTROHOTOR Filed June 15. 1922 Patented July 29, 1924.

UNITED STATES PATENT OF'FICZE.

CARL LOTT, OF HORG EN, SWITZERLAND.

DEVICE FOR DRIVING SHAFTS AT A LOW AND UNIFORM SPEED BY AN ELECTRO- MOTOR.

Application filed June 15, 1922. Serial No. 568,538.

To aZZ whom it may concern:

Be it known that I, CARL Lor'r, a citizen of the Swiss Confederation, residing at Bergstrasse Horgen. Canton Zurich, Switzerland, have invented new and useful Improvements in Devices for Driving Shafts at aLow and Uniform Speed by an Electromotor, of which the following is a specification.

In connection with the electric driving of slowly running shafts, particularly in the driving of record disc tables of talking machines, a series of requirements cannot be fulfilled by the means hitherto employed. A record disk has to run at an uniform speed over a long time and for every single revolution, whichis difficult to obtain as the low speed of the disk prevents the use of the momentum of the rotating disk table as a speed regulator.

The speed of the shafts should be independent of the variations of potential;

of the changes of temperature; of the surroundings, as well as of the heating of the windings and of variations in the magnetic quality or behaviour of the iron of the electric motor. Finally absolute noiselessness and freedom of the record disc from vibrations, which would cause noises in the sound box is required.

The quick running motors hitherto employed, which work with transmission gear on the record disc shaft, have some or all of the faults indicated.

According to this invention slowly rotat-. ing shafts and particularly record disc shafts are driven direct and slowly by an electric motor without intermediate gear, the stator field or the rotor field or both fields of the motor being supersaturated. The motor has a great internal resistance which consumes the greater part of the voltage. I use preferably series motors which might be used with continuous or alternating current but shunt motors may be used to obviate the faults mentioned. By supersaturation I wish to denote an iron having a density of lines of force of 20000 and more Gauss. By this high magnetizing I obtain the condition that variations of the exciting current in wide limits do not produce any considerable variations of the field and practically no variations of the torque. Owing to the supersaturation and the high internal resistance the current consumed by the motor is quite independent of the speed of rotation and remains constant not only at any speed but even when the motor is at rest. In alternating current .motors the reactance of the windings is added to the internal ohmic resistance.

As according to this invention, the internal resistance is great, in order to lessen the influence of the variations of potential on the number of revolutions the degree of efliciency is rather low but other advantages 7 yoke, n is the shaft and c the record disc table whilst 1* represents the centrifugal regulator, which can be adjusted by means of a lever h to effect more or less braking effect, whereby the speed of the sound disc is regulated.

Having now particularly described and ascertained the nature of the invention, and in what manner the same is to be performed I declare. that What I claim is:

Electric device for direct driving of shafts at low and uniform speeds, comprising an electromotor with its armature mounted upon said shaft and a centrifugal brake governor for said electromotor, and in which the magnetic field of the electromotor is supersaturated to a density of lines of force of 2-0000 and over per cmF, substantially as and for the purpose set forth.

In Witness whereof I aflix my signature.

CARL LOTT.

Witnesses:

E. HoL'rznRMAN, ARTHUR SoHRornnR. 

